Hi, I already did the stress test twice, the other day and yesterday, All the results are passed. My BIOS is updated to 1.2.6 and all drivers are update. 

HWMonitor at the first 2 minutes of  booting up the pc http://imgur.com/a/F7QRM

Cities Skylines at HIGH http://imgur.com/a/xq2YV

GTA 5 at HIGH

I opened up the case and the smell seems like coming from the CPU, though GPU and CPU are hot.

Hi, I can open the case, but I can't separate all the components to find where the burning smells is due to I might not be able to put them back together. Anyhow, I already did use HWMonitor and updated my BIOS to 1.2.6, every driver is updated. I just booted up my pc and this is my HWMonitor  

Cities Skylines at HIGH settings 

GTA 5 at HIGH settings  

I tried the stress test and the full test, and everything was passed.

Well, I opened up my case just right now, I didn't see any plastic inside. I just hope nothing is burning inside and I hope that burning plastic smell is just normal because my x51 is new.